I don't think that is true. Tuner Ready...that's kinda hasty. But, in regards to the Cobb fp16 acn map. Follow what they want for the map or your not likely to get good results. I highly doubt a BOV is in their specs. You probably have a leak of some sort... I can't say where or which end of the turbo. But, I'd do a leak test. Plus, are you reving up to 3.5k and letting off...then feeling the leak? If so, that's what it is suppost to do. BOV do not benefit a subaru in any regard though. The air induction system in our cars is what's referred to a closed loop induction system. Basically, any excess gets returned to the intake by a by-pass valve (BPV). It's not mean to run as open loop and let the excess vent to atmosphere. In short...get rid of the BOV.
Edit: If your holding the RPMs at 3.5 and still feeling a leak out of the BOV. Then, that is a leak that needs to be corrected. Probably a bad gasket at the connection point or a POS BOV. Sorry...but, BOVs are a subject of flaming in most cases.